(Reuters) - Britain has decided to cooperate with the United States on a release of strategic oil stocks that is expected within months, two British sources said, in a bid to prevent fuel prices choking economic growth in a U.S. election year.

A formal request from the United States to the UK to join forces in a release of oil from government-controlled reserves is expected "shortly" following a meeting on Wednesday in Washington between President Barack Obama and Prime Minister David Cameron, who discussed the issue, one source said.

Britain would respond positively, the two sources said.

Details of the timing, volume and duration of a new emergency drawdown have yet to be settled but a detailed agreement is expected by the summer, one of the sources said.

Other countries may also be approached by Washington to contribute, a further source said, Japan among them.